Add tools/maint/create_release.py. NFC (#17876)

docs/process.md

@@ -85,9 +85,10 @@ How:
 1. [Tag][emscripten_tags] the `emscripten` repo with the new version number, on
    the commit referred to in the [DEPS][DEPS] (or DEPS.tagged-release) file
    above.
-1. Update [`emscripten-version.txt`][emscripten_version] and
-   [`ChangeLog.md`][changelog] in the emscripten repo to refer the next,
-   upcoming, version. An example of this PR is emscripten-core/emscripten#17439.
+1. Run the `tools/maint/create_release.py` tool in the emscripten repo to update
+   [`emscripten-version.txt`][emscripten_version] and
+   [`ChangeLog.md`][changelog].  An example of such PR is
+   emscripten-core/emscripten#17439.
 
 Major version update (1.X.Y to 1.(X+1).0)
 -----------------------------------------

tools/maint/create_release.py

@@ -0,0 +1,75 @@
+#!/usr/bin/env python3
+# Copyright 2022 The Emscripten Authors.  All rights reserved.
+# Emscripten is available under two separate licenses, the MIT license and the
+# University of Illinois/NCSA Open Source License.  Both these licenses can be
+# found in the LICENSE file.
+
+from datetime import datetime
+import os
+import subprocess
+import sys
+
+script_dir = os.path.dirname(os.path.abspath(__file__))
+root_dir = os.path.dirname(os.path.dirname(script_dir))
+
+sys.path.append(root_dir)
+from tools import shared, utils
+
+
+def main():
+  if subprocess.check_output(['git', 'status', '-uno', '--porcelain'], cwd=root_dir).strip():
+    print('tree is not clean')
+    return 1
+
+  shared.set_version_globals()
+
+  old_version = [shared.EMSCRIPTEN_VERSION_MAJOR, shared.EMSCRIPTEN_VERSION_MINOR,
+                 shared.EMSCRIPTEN_VERSION_TINY]
+  new_version = list(old_version)
+  new_version[2] += 1
+
+  old_version = '.'.join(str(v) for v in old_version)
+  new_version = '.'.join(str(v) for v in new_version)
+
+  print('Creating new release: %s' % new_version)
+
+  version_file = os.path.join(root_dir, 'emscripten-version.txt')
+  changelog_file = os.path.join(root_dir, 'ChangeLog.md')
+
+  old_content = utils.read_file(version_file)
+  utils.write_file(version_file, old_content.replace(old_version, new_version))
+
+  changelog = utils.read_file(changelog_file)
+  marker = f'{old_version} (in development)'
+  pos = changelog.find(marker)
+  assert pos != -1
+  pos += 2 * len(marker) + 1
+
+  # Add new entry
+  today = datetime.now().strftime('%m/%d/%y')
+  new_entry = f'{old_version} - {today}'
+  new_entry = '\n\n' + new_entry + '\n' + ('-' * len(new_entry))
+  changelog = changelog[:pos] + new_entry + changelog[pos:]
+
+  # Update the "in development" entry
+  changelog = changelog.replace(f'{old_version} (in development)', f'{new_version} (in development)')
+
+  utils.write_file(changelog_file, changelog)
+
+  branch_name = 'version_' + new_version
+
+  # Create a new git branch
+  subprocess.check_call(['git', 'checkout', '-b', branch_name], cwd=root_dir)
+
+  # Create auto-generated changes to the new git branch
+  subprocess.check_call(['git', 'add', '-u', '.'], cwd=root_dir)
+  subprocess.check_call(['git', 'commit', '-m', new_version], cwd=root_dir)
+
+  print('New relase created in branch: `%s`' % branch_name)
+
+  # TODO(sbc): Maybe create the tag too, and even push both to `origin`?
+  return 0
+
+
+if __name__ == '__main__':
+  sys.exit(main())